IMMUNE-COMPLEXES AND COMPLEMENT HYPERCATABOLISM IN PATIENTS WITH LEPROSY

Abstract

The occurrence of immune complexes in the serum and the level of the C3 [3rd complement component] breakdown product C3d in the plasma from patients with leprosy were studied by quantitative methods, and the results were compared in various forms of the disease. These studies were performed on 62 samples from 26 patients. The serum 125I-C1q binding activity was increased by more than 2 SD, as compared to the normal values, in most of the sera from patients with erythema nodosum leprosum (ENL) (80%) and uncomplicated lepromatous leprosy (82%) and in the sera from patients with tuberculoid leprosy (58%). In vitro studies suggested that immune complexes involving mycobacterial antigens were present in leprosy sera. An increased C3d level (> 2 SD) was found in most of the plasma from patients with ENL (70%), but rarely in the plasma from patients with uncomplicated lepromatous leprosy (18%) and never in tuberculoid leprosy patients'' plasma. The absence of a significant correlation between the 125I-C1q binding activity and the C3d level in leprosy patients may suggest that extravascular immune complexes are involved in the complement activation occurring in ENL. The quantitation of C3d in plasma may be of some practical interest in the early diagnosis of ENL complications of leprosy.